Power switch

ABSTRACT

A power switch includes a fixed contact member 13 to which a fixed contact 14 is joined, a movable contact member 5 to which there is joined a movable contact 6 movable into and out of contact with the fixed contact 14 of the fixed contact member 13, a commutation electrode 3 for transferring an arc generated when the fixed contact 14 and the movable contact 6 are separated, and a grid 2 for extinguishing the arc transferred on the commutation electrode 3, the commutation electrode 3 having a recess 17 for allowing the movable contact 6 to move out of contact with the fixed contact 14 and so that the movable contact member 5 can move toward the fixed contact member 13, the commutation electrode 3 having an end extending parallel to the grid 2 and a slit 16, 19 extending continuously from the recess 17 to a portion parallel to the grid 2.  The arc generated when the movable contact 6 is separated from the fixed contact 14 can be transferred at high speed toward the slit 16, 19 by a current produced in the commutation electrode 3.

TECHNICAL FIELD

The present invention relates to a power switch such as anelectromagnetic contactor, and more particularly to an improvement in acommutation electrode thereof.

As shown in FIGS. 1(a) and 1(b), a conventional electromagneticcontactor has a commutation electrode 3 disposed around an end of amovable contact member 5 to which a movable contact 6 is joined. FIGS.2(a) and 2(b) illustrate a fixed contact member 13 disposed inconfronting relation to the movable contact member 5 and an arc rubber15 attached to the fixed contact member 13. A fixed contact 14 is joinedto the fixed contact member 13. The movable contact 6 of the movablecontact member 5 is movable into and out of contact with the fixedcontact 14.

The movable contact member 5 has an intermediate portion connected to aknown electromagnetic drive device. The movable contact 6 is joined toeach end of the movable contact member 5, and the fixed contact members13 are provided respectively for the movable contacts 6.

FIGS. 1(a) and 1(b) are perspective and enlarged fragmentary plan views,respectively, schematically showing the commutation electrode 3, themovable contact member 5, and the movable contact 6. The fixed contactmember 13, the fixed contact 14, and the arc runner 15 in FIGS. 1(a) and1(b) are schematically shown in FIGS. 2(a) and 2(b) at an enlargedscale.

In the conventional electromagnetic contactor having the commutationelectrode 3, when the fixed contact 14 and the movable contact 6 areseparated, an end of an arc generated between these contacts istransferred from the movable contact 6 to the commutation electrode 3,while the other arc end is transferred from the fixed contact 14 to thearc runner 15. The transferred other end of the arc is moved on the arcrunner 15 toward the other end thereof until finally the arc isextinguished between the parallel portion of the arc runner 15 and thecommutation electrode 3 confronting the same.

With the commutation electrode 3 in the conventional electromagneticcontactor being shaped as shown in FIGS. 1(a) and 1(b), when an arc legis produced at a position P as shown in FIGS. 1(a) and 1(b), currentcomponents i1, i2 flowing from the commutation electrode 3 into the arclegs are of substantially the same value, and an arc current is equal tothe sum i of the current components i1, i2 (i=i1+i2). In FIG. 1(b), thecommutation electrode 3 has a prescribed thickness (though it is omittedfrom illustration in FIG. 1(a)) across its width. In FIG. 1(b), l1, l2denote the distances from the ends of the commutation electrode 3 to theposition P where the arc is produced. Since the force F1 imposed by thecurrent i1 on the arc is larger than the force F2 imposed by the currenti2 on the arc, the arc is driven in the direction of the force F whichis the combination of the forces F1, F2. Therefore, the arc is broughtinto direct contact with an arc box of synthetic resin accommodating thecommutation electrode 3 and the movable contact member 5, thus leavinggreat damage on the arc box.

DISCLOSURE OF THE INVENTION

Accordingly, it is an object of the present invention to provide a powerswitch having a prescribed recess (slit) for preventing an arc box frombeing damaged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) and 1(b) are enlarged fragmentary views of a movable contactmember and a commutation electrode, the view showing a conventionalelectromagnetic contactor;

FIGS. 2(a) and 2(b) are enlarged fragmentary views of a fixed contactmember and an arc runner of the conventional electromagnetic contactor;

FIG. 3 is a side elevational view, partly in cross section, of anelectromagnetic contactor according to an embodiment of the presentinvention;

FIG. 4 is a fragmentary perspective view of a commutation electrode anda movable contact member of the electromagnetic contactor of theinvention;

FIG. 5 is a righthand side elevational view, partly in cross section, ofan electromagnetic contactor according to another embodiment of thepresent invention;

FIG. 6 is an enlarged fragmentary vertical cross-sectional view of theelectromagnetic contactor of FIG. 5;

FIG. 7 is a view explanatory of operation of the arrangement illustratedin FIG. 6;

FIG. 8 is a fragmentary perspective view of another embodiment of thepresent invention, with a modified commutation electrode; and

FIG. 9 is an enlarged fragmentary vertical cross-sectional view showinga nofuse circuit breaker to which the present invention is applied.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described hereinbelow.

FIGS. 3 and 4 illustrate an embodiment in which the present invention isapplied to an electromagnetic contactor. Designated at 1 is an arc boxmade of a heatresistant material for extinguishing arcs. As many grids 2and commutation electrodes 3 of magnetic metal as there are the phasesof circuits to be opened and closed are disposed in and fixed to the arcbox 1. Denoted at 4 is a cross bar, 5 a movable contact member, 6 amovable contact attached to each end of the movable contact member 5, 7a holder for the movable contact member, 8 a holder spring support, 9 acontact member spring, and 10 a stopper. The contact member spring 9 isdisposed under compression between the lower portion of the stopper 10and the holder spring support 8. The holder spring support 8 is heldagainst the upper surface of the movable contact member holder 7, andthe upper surface of the movable contact member 5 is held against thelower surface of the movable contact member holder 7. Designated at 12is a terminal fastened by screws or the like to a fixed contact member13 to which a fixed contact 14 is joined. The movable contact member isconnected through the contact member spring 9 to a known built-inelectromagnetic drive device (not shown).

Such contact mechanisms are disposed symmetrically with respect to thecross-sectional plane A--A. There are as many contact mechanisms as thenumber of phases of circuits to be opened and closed, the contactmechanisms being arranged in a direction normal to the sheet of thefigures. Indicated at 15 is an arc runner, and 16 a slit defined fromthe lower end to the upper end of the commutation electrode 3 and havinga prescribed length toward the righthand end as shown in FIG. 4. Thecommutation electrode 3 has a prescribed thickness though it is omittedfrom illustration in FIG. 4.

The commutation electrode 3 has at least four surfaces which willhereinafter be referred to as a first plate 3A, a second plate 3B, athird plate 3C, and a fourth plate 3D, respectively. The plates 3A, 3B,3C, 3D used in the present invention are not limited to those havingflat surfaces, but include those having curved surfaces, for example.

Designated at 17 is a large recess extending from the second plate 3B tothe fourth plate 3D for allowing the movable contact member 5 to movetherein. The slit 16 extends from the first plate 3C to the third plate3A in contiguous relation to the recess 17.

When the contacts of the electromagnetic contactor are separated, an arcgenerated between the contacts is transferred to the second plate 3B ofthe commutation electrode 3 and the arc runner 15, and then moved fromthe second plate 3B onto the third plate 3C and goes on and along thethird plate 3C and the arc runner 15. Finally, the arc C exists betweenthe first plate 3A, the grids 2, and the arc runner 15. At this time,one leg of the arc C is positioned at a point P on the third plate 3C,and the other arc leg is located in a prescribed position (not shown) onthe arc runner 15. A current related to the arc C flows in the directionof the arrow in FIG. 4. Denoted at i is an arc current, and i=i1+i2.

An arc driving force F1 due to the current i1 is generated laterallyalong a parallel portion of a vertical plate 3C of the commutationelectrode 3 as illustrated. An arc driving force F2 due to the currenti2 is generated downwardly along a vertical direction of the commutationelectrode 3 as illustrated. The force F produced by combining the forcesF1, F2 is necessarily directed toward wall of the arc box (which isnormal to the commutation electrode 3 and adjacent to the side surfacethereof) within a plane including the commutation electrode 3, forthereby moving the arc leg on the point P in a direction toward a pointQ.

For the same reason, when an arc leg is transferred to a point R on thecommutation electrode 3, an arc driving force generated by a currentflowing through the commutation electrode 3 forcibly moves the arc legfrom the point R to a point S.

As a consequence, the arc leg is moved in the vicinity of the slit 16 inthe commutation electrode 3 without deviating therefrom, so that the arcwill be prevented from contacting an arc box wall and hence fromdamaging the arc box.

While in the above embodiment the slit 16 is of a rectangular shape, theslit is not limited to such a shape.

With the embodiment of the invention as described above, the provisionof the slit 16 in the commutation electrode is effective in preventingthe arc from damaging the arc box 1.

FIGS. 5 through 7 illustrate another embodiment in which the presentinvention is applied to an electromagnetic contactor.

Those parts which are idential to those shown in FIGS. 3 and 4 aredenoted by identical reference characters. Denoted at 1a a are a numberof holes defined in a side wall of an arc box 1, 20 a porous metal platedisposed in covering relation to the holes 1a, 21 a fixed laminated ironcore composed of silicon steel plates, 22 a control coil for producing adriving force to attract a movable iron core 24 connected to a cross bar4 against the spring force, and 23 a terminal screw mounted on aterminal 12 for connecting a wire.

The electromagnetic contactor shown in FIG. 5 is symmetrical in shape,and a right hand portion thereof is illustrated in cross section.

FIGS. 6 and 7 show the commutation electrode 3 at an enlarged scale. Thecommutation electrode 3 includes a first plate 3A extending parallel tothe surface of a fixed contact 14 and spaced a prescribed distance froma fixed contact member 13 with grids 2 interposed between the firstplate 3A and the fixed contact member 13, a second plate 3B extendingparallel to the surface of the fixed contact 14 and positioned betweenthe surface of a movable contact member 5 to which no movable contact 6is joined and the fixed contact member 13 at the time the movablecontact 6 and the fixed contact 14 are separated, a third plate 3Cconnecting the first and second plates 3A, 3B to each other, and afourth plate 3D extending from the second plate 3B in the direction inwhich the movable contact 6 is separated from the fixed contact 14. Thecommutation electrode 3 also has a recess 17 defined in confrontingrelation to the movable contact member 5 and extending from the fourthplate 3D to the second plate 3B. Denoted at 19 is a slit extending fromthe recess 17, across the third plate 3C toward a free edge 3G of thefirst plate 3A to divide the first and third plates 3A, 3C into halves.

Circuit breaking operation will now be described. When the coil 22 shownin FIG. 5 is de-energized, the movable iron core 24 is separated fromthe fixed iron core 21 by a tripping spring (not shown) to separate themovable contact 6 from the fixed contact 14, whereupon an arc 30 isgenerated between the contacts 6, 14. The arc 30 is attracted to thegrids 2 of a magnetic material and transferred between the commutationelectrode 3 and the arc runner 15 under the magnetic field flowingthrough the movable contact member 5 and the fixed contact member 13, asshown at 30A in FIG. 6. The arc 30A is attracted by the magnetic grids 2and driven by the magnetic field generated by the current flowingthrough the commutation electrode 3 and the arc runner 15, as shown at30B. The arc 30B is then driven by the first plate 3A and the end of thearc runner 15, as shown at 30C, and the arc 30C is then extinguished. Anarced gas produced when the arc is produced is cooled while passingthrough the pores in the porous metal plate 20, and is discharged out ofthe holes 1a in the arc box 1.

When one leg of the arc 30A is produced at a point A as shown in FIG. 7,there is no current IC flowing through a path ACP because of the slit19, and all current flowing through the commutation electrode 3 flowsthrough a path ABP as a current IB. Therefore, the arc 30A is forciblydriven to the right in FIG. 7 against being stuck at the point P. Sincethe arc 30A is driven at a high speed, the arcing time is shortened andthe arc energy is reduced for increased circuit breaking performance.

FIG. 8 is a perspective view of a commutation electrode and a movablecontact member according to still another embodiment of the presentinvention. This embodiment differs from that of FIG. 7 in that the slit19 is slightly wider in the third plate 3C adjacent to the second plate3B. This arrangement has the same advantages as those of FIG. 7.

In the above embodiments, the present invention is applied to anelectromagnetic contactor. However, the present invention is alsoapplicable to a no-fuse circuit breaker.

FIG. 9 is explanatory of a process of extinguishing an arc produced in ano-fuse circuit breaker to which the present invention is applied.Denoted at 40 is a shaft about which a movable contact member 5 isrotatable, and 41 a flexible stranded wire connecting a commutationelectrode 3 to the movable contact member 5. The movable contact member5 is rotatable about the shaft 40 for opening and closing the contacts6, 14. Although not shown, the no-fuse circuit breaker is associatedwith an overcurrent detector and a control mechanism.

Operation will now be described. When an overcurrent flows, it isdetected by the overcurrent detector which causes the control mechanismto separate the movable contact 6 from the fixed contact 14, producingan arc 30. The arc 30 is attracted to metal extinguishing plates 2 anddriven by the magnetic field produced by a current flowing through themovable contact member 5 and the fixed contact member 13 so that the arc30 is moved through 30A, 30B, and 30C and then extinguished by the metalextinguishing plates 2, a process which is the same as that employed inthe embodiment shown in FIGS. 5 through 7. In FIG. 9, a slit 19 extendsfrom a recess 17 through a third plate 3C to a free end 3G of a firstplate 3A to divide the first and third plates 3A, 3C into halves.Therefore, for the same reason as that of the embodiment partly shown inFIGS. 5 through 7, the arc 30 can quickly be driven for increasedcircuit breaking performance. The slit 19 may be the same shape as thatof the slit shown in FIG. 8.

While in each of the foregoing embodiments the recess 17 extends fromthe fourth plate 3D to the second plate 3B, it may extend from thefourth plate 3D through the second plate 3B to the third plate 3C forattaining the same advantages as those of the foregoing embodiments.

As described above, the slit extending from the recess through the thirdplate to the free end of the first plate to divide the first and thirdplates into halves is effective in quickly driving an arc generatedbetween the contacts, with the result that the circuit breakingperformance can be increased.

We claim:
 1. A power switch comprising a fixed contact member (13) to which a fixed contact (14) is joined, a movable contact member (5) to which there is joined a movable contact (6) movable into and out of contact with the fixed contact for the fixed contact member, a commutation electrode (3) for transferring an arc generated when the fixed contact and the movable contact are separated, and a grid (2) for extinguishing the arc transferred on the commutation electrode, said commutation electrode having a recess (17) for allowing said movable contact to move out of contact with said fixed contact so that said movable contact member can move toward the fixed contact member, said commutation electrode having an end extending parallel to said grid and a slit (16, 19) extending continuously from the recess to a portion parallel to said grid, wherein said commutation electrode has a first plate (3A) extending parallel to the surface of said fixed contact and spaced a prescribed distance from said fixed contact member, a second plate (3B) extending parallel to the surface of said fixed contact and positioned between the surface of said movable contact member to which no movable contact is joined and said fixed contact member at the time said movable contact and said fixed contact are separated, a third plate (3C) connecting said first and second plates to each other, and a fourth plate (3D) extending from said second plate in the direction in which said movable contact is separated, said recess extending from said fourth plate to said second plate, said first plate being said portion parallel to said grid, said slit extending continuously from said recess through said third plate to said first plate.
 2. A power switch according to claim 1, wherein said slit extends continuously from said recess to an end of said first plate to divide said third and first plates into halves.
 3. A power switch according to claim 1, wherein said grid is made of a magnetic metal, there being a plurality of such grids.
 4. A power switch according to claim 1, wherein said recess and said slit are defined centrally in said commutation electrode in the transverse direction thereof and extend from said fourth plate through said second and third plates to said first plate to divide these plates into two equal portions. 